Critical to the fuel efficiency and the emissions of gas turbine engine is the combustion process. Appropriate mixing of fuel and air, including atomization of the fuel is important for generation of complete fuel combustion for purposes of efficiency and emissions control. Air blast fuel nozzles generally utilize particularly directed blasts of airflow to impinge upon and atomize the fuel prior to ignition and combustion thereof. Often atomization of the fuel flow occurs in a premixing chamber prior to introduction into the major portion of the combustion chamber. Not only the extent of atomization, as determined by the average fuel droplet size, but also the spray angle of the atomized mixture is important for good combustion processes in the primary zone of the combustion chamber. In this respect, primary airflow is introduced into the primary combustion zone wherein combustion initiates.
While a large volume of primary air is desirable for a variety of thermodynamic and combustion reasons, the magnitude of the primary air must necessarily be limited in a manner maintaining appropriate residence time in the primary zone to obtain a continuous combustion process and avoid flameout therein. To increase residence time in the primary zone it is generally known that swirling of the primary airflow contributes to appropriate combustion. The known arrangements for inducing axial swirl in the primary airflow leads to cumbersome, heavy and expensive structures. Additionally, attempts to introduce both radial and axial primary airflows into the primary zone of the combustor chamber dramatically increases complexity of the overall structure.